1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to a hard disk drive having a disk locking apparatus locking a disk so that the disk is not rotated when the hard disk drive is not operated, for example, when the hard disk drive is being carried/transported.
2. Description of the Related Art
A hard disk drive (HDD), which is one of the auxiliary memory devices of a computer, reads or records data with respect to a magnetic disk by using a magnetic head. Recently, various research and development efforts have realized high speed, high capacity, low vibration and low noise hard disk drives.
FIG. 1 is a top view illustrating a conventional hard disk drive. FIG. 2 is an enlarged perspective view illustrating part of the hard disk drive of FIG. 1. Referring to FIGS. 1 and 2, a hard disk drive includes a magnetic disk (hard disk) 20 that is a recording medium where data is recorded, a spindle motor 30 installed on a base plate 10 and rotating the disk 20, and an actuator 40 having a magnetic head 41 for recording and reproducing data with respect to the disk 20.
One or a plurality of disks, separated a predetermined distance from each other, are installed as the disk 20 and rotated by the spindle motor 30. A parking zone 21 where a slider 42 is accommodated when power is turned off is provided at the inner circumferential side of the disk 20. A data zone 22 where a magnetic signal is recorded is provided at the outer side of the parking zone 21. A servo signal for indicating the position of the information to be recorded is recorded in advance on tens of thousands of tracks along the circumference of the disk 20.
The actuator 40 pivots around a pivot shaft 47 installed on the base plate 10 by a voice coil motor 48. The actuator 40 includes an arm 46 coupled to the pivot shaft 47 to be capable of pivoting and a suspension 44 installed at the arm 46 and supporting the slider 42 where the magnetic head 41 is mounted to be elastically biased toward a surface of the disk 20.
When the power of the hard disk drive is turned off, the slider 42 is accommodated in the parking zone 21 of the disk 20 by an elastic force of the suspension 44. When the power is turned on and the disk 20 starts to rotate, lift is generated due to air pressure and the slider 42 is lifted. The slider 42 in a lifted state is moved to the data zone 22 of the disk 20 as the arm 46 pivots. The slider 42 moved to the data zone 22 of the disk 20 maintains a lifted state at a height where the lift by the rotation of the disk 20 and the elastic force by the suspension 44 are balanced. Thus, the magnetic head 41 mounted on the slider 42 records and reproduces data with respect to the disk 20 while maintaining a predetermined distance from the disk 20 that is rotating.
As described above, one or a plurality of disks are installed in the hard disk drive. Conventionally, four or more disks are installed in a hard disk drive to increase a data storage capacity. However, recently, as a surface recording density of a disk has increased, one or two disks can store a sufficient amount of data. Thus, recent hard disk drives mainly have one or two disks only.
FIGS. 3A through 3C are side views illustrating part of the hard disk drive shown in FIG. 1. First, FIG. 3A shows a 1-channel type hard disk drive using only one side of a disk to store data. Referring to FIG. 3A, the disk 20 is installed at the spindle motor 30 supported by the base plate 10 to be capable of rotating. Two arms 46a and 46b are coupled to the pivot shaft 47 supported by the base plate 10 to be capable of pivoting. As shown in FIG. 3A, when the bottom surface of the disk 20 is used as a recording surface, the suspension 44 is installed only at an end portion of the first arm 46a disposed under the disk 20 of the two arms 46a and 46b and the slider 42 where the magnetic head is mounted is installed at an end portion of the suspension 44. A dummy head 49 is installed at an end portion of the second arm 46b disposed above the disk 20 separated a predetermined distance from the surface of the disk 20. The dummy head 49 prevents unbalance of forces generated at both sides of the disk 20 during rotation of the disk 20, and has a weight approximately corresponding to the sum of weights of the suspension 44 and the slider 42.
Japanese Patent Laid-Open Publication No. hei 11-25403 entitled “Magnetic Recording and Reproduction Apparatus” discloses a 1-channel type hard disk drive. In the hard disk drive, a lift slider is installed at one side of a disk and a dummy slider is arranged at the opposite position. The dummy slider prevents warping of a relatively thin disk having a thickness of 0.5–1.2 mm, performing the same function as the dummy head shown in FIG. 3A.
FIG. 3B shows a 2-channel type hard disk drive in which both side surfaces of a disk are used for storing data. Referring to FIG. 3B, when both side surfaces of the disk 20 are used as recording surfaces, the suspension 44 is installed at the end portion of each of the two arms 46a and 46b and the slider 42 having the magnetic head mounted thereon is installed at the end portion of each suspension 44. Thus, the 2-channel type hard disk drive does not need the dummy head 49 shown in FIG. 3A.
However, as shown in FIG. 3C, three arms 46a, 46b, and 46c can be installed at the 1-channel and 2-channel type hard disk drive shown in FIGS. 3A and 3B, respectively, in which the 1-channel and 2-channel hard disk drives use parts in common (e.g., arm 46b is shared). In this case, a dummy head may be installed at the end portion of the third arm 46c where the suspension 44 is not installed. FIG. 3C shows a 3-channel type hard disk drive using three side surfaces of two disks for storing data. Referring to FIG. 3C, two disks 20a and 20b are installed at the spindle motor 30 supported by the base plate 10 to be capable of rotating. Three arms 46a, 46b, and 46c are coupled to the pivot shaft 47 supported by the base plate 10 to be capable of pivoting. As shown in FIG. 3C, when both side surfaces of the first disk 20a and the bottom surface of the second disk 20b are used as recording surfaces, the suspension 44 is installed at each end portion of the first arm 46a disposed under the first disk 20a and the end portion of the second arm 46b disposed between the first disk 20a and the second disk 20b. The slider 42 where the magnetic head is mounted is installed at the end portion of each suspension 44. A dummy head 49 is installed at the end portion of the third arm 46c disposed above the second disk 20b. 
In the conventional hard disk drives having the above structures, vibrations are generated in a rotating disk due to defective parts of the spindle motor, defective assembly of the disk, and irregular flow of air in the hard disk drive. The vibrations can be divided into RRO (repeatable runout) that is a component repeated for each rotation, and NRRO (non-repeatable runout) that is not repeated for each rotation. RRO which repeats regularly can be compensated for by a servo control system to a degree, however, NRRO is difficult to compensate for in advance.
The vibrations of the disk, in particular, NRRO, is known to be caused mainly by a defect in a ball bearing in the spindle motor. The defect of the ball bearing of the spindle motor is frequently generated when the hard disk drive is carried/transported. When the hard disk drive is being carried, the disk can slightly rotate, so that the ball bearing in the spindle motor is partially abraded. That is, since lubricant is not uniformly distributed when the hard disk drive is not operated, if the stopped disk moves or rotates during transportation, a portion of the ball bearing where the lubricant is not provided can have friction with a shaft or a hub of the spindle motor, so that the surface of the ball bearing can be damaged. Further, recently, the thickness of the disk has increased roughly from 1 mm to 1.27 mm to reduce disk vibration. Accordingly, as the weight of the disk increases, the damage to the ball bearing by the rotation of the heavier disk increases.
In the meantime, in the case of an FDB (fluid dynamic bearing), since the size of a groove of a journal bearing or a thrust bearing is several micrometers, it can be easily damaged by a rotation of the disk when the disk drive is not operated, which typically can be generated when the hard disk drive is carried/transported. When the groove is damaged, since a pressure is not generated appropriately from the groove, a function of the FDB is not smoothly performed. The abrasion phenomenon occurring in a stopped bearing by an external vibration is referred to as fretting.
The abrasion phenomenon of the stopped bearing mainly occurs in the 1-channel type hard disk drive shown in FIG. 3A. Since the rotation of the disk 20, during which the hard disk drive is not operated, is prevented only by the one slider 42 contacting the parking zone of the lower surface of the disk 20, the disk 20 can be easily rotated when a small amount of external vibration is applied to the disk 20. However, in the 2-channel type hard disk drive shown in FIG. 3B, since two sliders 42 contact both side surfaces of the single disk 20 and elastic forces are acting in the opposite directions by the suspensions 44 at both sides of the disk 20, the disk 20 is not easily rotated by an external vibration. Also, in the 3-channel type hard disk drive shown in FIG. 3C, since the two disks 20a and 20b are supported by contacting the three sliders 42, the disk 20a is not easily rotated as the disk 20b. 
As described above, when the bearing of the spindle motor is damaged by the rotation of the disk when the hard disk drive is carried/transported, vibrations are generated in the disk during the operation of the hard disk drive. The disk vibrations deteriorate data recording and reproduction capability of the magnetic head, so that the performance of the hard disk drive is badly affected. Also, the disk vibrations generate noise causing a work environment nuisance. Further, occurrences of fretting have increased because of increased recording density of each disk causing an increase in manufacture of 1-channel type hard disk drives, which are more susceptible to fretting.